Borohydride-Assisted Surface Activation of Co(3)O(4)/CoFe(2)O(4) Composite and Its Catalytic Activity for 4-Nitrophenol Reduction

[Image: see text] Surface activation of catalysts is known to be an efficient process to enhance their activity in catalytic processes. The activation process includes the generation of oxygen vacancies, changing the nature of the catalyst surface from acidic to basic and vice versa, and the reduction of catalyst surface by H(2). On the other hand, magnetically separable catalysts are highly beneficial for their utilization in water or biological fluid-based catalytic processes, as they can be easily guided to the target site and recovered. Here, we present the fabrication of CoFe(2)O(4) and composites of Co(3)O(4)/CoFe(2)O(4)/α-Fe(2)O(3) and Co/CoFe(2)O(4)/α-Fe(2)O(3) through solution combustion process to utilize them as catalysts for 4-nitrophenol (4-NP) reduction. Although none of the as-prepared CoFe(2)O(4) and Co(3)O(4)/CoFe(2)O(4) was seen to be active in 4-NP reduction reaction, the surface of the composite gets activated by borohydride (NaBH(4)) treatment to act as a highly active catalyst for 4-NP reduction. X-ray photoelectron spectroscopy of the composite revealed the formation of metal-hydroxide (M–O–H) species of both Co and Fe at its surface due to borohydride treatment. The mechanism of the surface activation and the dynamics of 4-NP reduction of the surface-activated composite have been studied, proposing a possible pathway for the reduction of 4-NP.